Due to an increasing concern for the environment, there is a continuing effort to reduce the pollution created by internal combustion engines. In this regard, efforts have been directed towards the reduction of particulate matter exhausted from diesel engines. One method for reducing such emissions is to place a trap or filter in the exhaust system which collects the particulate material. These traps are, however, relatively small and fill up rapidly. Cleaning of the traps can be accomplished by subjecting the trap to temperatures which decompose (burn) the collected particulate. To facilitate this process, it is advantageous that the ignition temperature of the particulate be as low as possible so that the particles start burning at the lowest possible temperatures. This lowering of ignition temperature can be accomplished by the addition of a combustion improver to the exhaust particulate. The most practical way to effect the addition of the combustion improver to the exhaust particulate is by adding the combustion improver to the fuel which when burned in the engine results in the exhaust particulate containing a combustion improver. Combustion improvers useful for this purpose are manganese or copper compounds. Manganese and copper compounds are both effective in reducing the ignition temperature of diesel engine exhaust particulate. Copper compounds, however, are more effective ignition temperature reducers than manganese compounds. While copper compounds are very effective ignition temperature improvers, their use can result in engine deposits. In accordance with the present invention, it has now been found that the ignition temperature reduction and propagation of the burning of exhaust particulate from internal combustion engines, particularly diesel engines, is improved along with a reduction in engine deposits.